Suppression of both autologous and allogeneic T-cell responses segregates with the CD4⁺CD25^brightFoxp3⁺ Tregs expanded by autologous, IDO-expressing, mature moDCs. (A) T cells harvested after two 6-day rounds of priming with autologous, mature moDCs were sorted cytofluorographically into CD4⁺CD25^bright, CD4⁺CD25^int, and CD4⁺CD25^neg subgroups, and (B) assessed for Foxp3 expression postsort. Data are from 1 representative experiment of 4. (C-D) Cytofluorographically sorted CD4⁺CD25^bright, CD4⁺CD25^int, and CD4⁺CD25^neg T cells were added to allogeneic MLRs composed of either fresh autologous moDCs and new allogeneic T cells (C) or fresh autologous T cells with new allogeneic moDCs (D). MoDC to responder T-cell ratio was 1:30 throughout, and candidate suppressor T-cell to responder T-cell ratios were 1:25 (□), 1:5 (▩), and 1:1 (▤). Controls included MLRs without suppressor cells (Ctrl^#1, ■) and moDCs cultured with candidate suppressor cells without responder T cells (Ctrl^#2, ). After 4 to 5 days' culture, responder T-cell proliferation was measured by [³H]TdR incorporation and compared with Ctrl^#1 (average of quadruplicate means ± SEM, n = 4 independent experiments; P value(s) indicated on each graph).